Luggage and bags Pack at least 1 pair of pants and a long sleeve shirt if you plan on going to Hawaii Volcanoes National Park at night or to the summit of Mauna Kea, both of which I highly recommend. You will have a jacket and gloves provided to you if you take one of the guided tours to the summit of Mauna Kea.
Clothing/Shoes/Weather Gear If you are going up to the summit of Mauna Kea, or if you're headed to Volcanoes National Park you will want to wear pants & a jacket. The Mauna Kea summit still has sub-freezing temperatures even during the summer. Volcanoes National Park had temperatures in the 50's at night when I was there in September, and Mauna Kea was cold ( 30 degrees) even with long pants, a winter parka, & heavy gloves.
Photo Equipment A camera with good nighttime capabilities would be preferable
Luggage and bags Snow gear to Hawaii?? Yes, if you love snow so much. We're having lots of snow at the summit of Mauna Kea (White Mountain) this winter. The view from the top is incredible when the summit is covered with snow. So, bring some warm clothes if you go up in your SUV or Truck.
Clothing/Shoes/Weather Gear Mitten; woolen hat; chap stick or vaseline gel for your lip. A pair of long john might be godsend.
Miscellaneous The air is very thin at the summit. Be sure to spend at least an hour at the visitor center on the way to the summit. Being acclimated to the high altitude condition is important for your health. At the visitor center, you (and your children) can learn about astronomy. It's a cool place.
Clothing/Shoes/Weather Gear In the winter months it is cooler than you think it will be. The nights are chilly and you need a wrap. It also rains a lot so take a ponch or umbrella. Enclosed toe walking shoes are a must if you go see the volcanos.